1. Field of the Invention
The present invention concerns downhole apparatus for use during production of hydrocarbons from an oil or gas well in which means are provided to insure proper distribution of corrosion inhibitor and the like within the well casing to an area below a well packer and for subsequent circulation of the inhibitor with the produced hydrocarbons through well tubing extending through the packer to the earth's surface.
2. Description of the Prior Art
An oil or gas well equipped with a packer substantially off bottom as seen, for example, in U.S. Pat. No. 4,031,955 entitled "Down-hole Inhibitor Injector" by Charles A. Ledet, will have completion fluid in the annulus above the packer and formation gas in the annulus below the packer. If non-corrosive, this gas presents no problems. If, however, the gas contains some corrodents such as H.sub.2 S, CO.sub.2, or water, the presence of the gas under the packer could cause severe problems. Unless equipped with very costly tubulars the corrosive gas can destroy the tubing and casing below the packer.
The Ledet patent discloses an assembly in which liquid corrosion inhibitor is flowed down through and into the annulus with the inhibitor solution passing through the packer. The packer assembly contains a valving apparatus and a circulation bypass for injection below the lower end of the packer assembly. Thus, to combat corrosion, corrosion inhibitor, as in the Ledet patent, can be jumped down the upper annulus and, using an injection assembly in conjunction with a packer, injected into the annulus below the packer. However, if gas is present in the lower annulus, the injected inhibitor will run down the pipe (tubing and/or casing) in rivulets. Such action will render the corrosion inhibition attempt useless, since to be effective the inhibitor must contact all of the pipe wall area. To be effective a device is needed that will maintain a column of inhibitor below the packer but will permit the inhibitor to be pumped through or passed through the device so that the inhibitor can go to bottom and into the tubing with the gas being produced.
In many wells, casing and tubing sizes will not permit the injection/packer assembly to be placed at bottom. Further, in deep wells, even if the injection/packer assembly could fit inside the casing, the wireline maintenance on the injection valve might not be possible because of the extreme difficulty in performing the deep wireline operations. To be of use in deep sour wells, the device must be virtually maintenance free, have as few moving parts as possible, be sturdy enough to withstand being run to 20,000 feet plus and permit the passage of the inhibitor while preventing the flip-flop of the inhibitor with the produced gas.
None of the prior art discloses an annular gas trap which effectively blocks the produced fluids from the pipe walls protected by the corrosion inhibitor.